Binder system for propellants and explosives



United States Patent BINDER SYSTEM FOR PROPELLAN TS AND EXPLOSIVES HenryT. Sampson, Urbana, 11]., assignor to the United The invention describedherein may be manufactured and used by or for the Government of theUnited States of America for governmental purposes without the paymentof any royalties thereon or therefor.

The present invention relates to improved binder compositions and thepreparation thereof. More specifically, it relates to an improved bindersystem for plastic-bonded explosives and composite propellants.

In the fields concerned with compressible explosives and cast compositepropellants it has been found that most of the binder materials in usehave high initial viscosity so that a high percentage of solidingredients cannot be combined or worked in and the product remaincompressible or castable. Most of the binders being used today,including polyurethanes, polysulfides, and nitrocellulose plastisols,require high curing temperatures in order to achieve the desiredphysical properties.

The general purpose of this invention is to provide a binder system forcomposite propellants and cast explosives which embraces all theadvantages of similarly employed binder systems and possesses none ofthe aforementioned disadvantages.

An object of the present invention is the provision of a bindercomposition which is compatible with a large number of high energyingredients used in explosives and propellants.

Another object is the provision of a low viscosity binder compositionwhich permits high loading of propellant and explosive ingredients.

A further object of the invention is the provision of a binder systemwhich will give increased energy to explosive and propellantcompositions.

Still another object is to provide a binder system which has goodadhesive properties.

Other objects, features and many of the attendant advantages of thisinvention will be readily appreciated as the same become betterunderstood by reference to the following detailed description.

Broadly, this invention contemplates a basic binder compositioncomprising about 30 to 40% by weight castor oil (CasO), about 11 to 15%by weight dipropylene glycol (DPG), about 20 to 30% by Weight2,4-tolylene diisocyanate (TDI) and about 15 to 35% by weighttrimethylol ethane trinitrate (TMETN).

. The binder composition is prepared by mixing castor oil, dipropyleneglycol and tolylene diisocyanate in a reaction flask for about twentyminutes. at 32 F. This reaction is highly exothermic and the viscosityof the reactants can be controlled by keeping the temperature below 120F. Since a by-product of the reaction is carbon dioxide, the reactionmust be carried out under vacuum if a bubble-free product is desired.However, it is possible to mix under normal pressure and degas theproduct after mixing. The trimethylol ethane trinitrate is added afterthe mixing step.. Atithis pointthe binder compositioniisreadyto be mixedwith explosive or propellant. ingredients and; .castinto a-suitablccontainer (rocket motor,

warhead). To. obtain; maximum physical properties, the

polymer should be cured for five days at 120 F. Shorter curing times ifdesired may be obtained by increasing the curing temperature or byadding a catalyst such as ferric acetyl acetonate in an amount notexceeding one part per 50 parts of polymer.

The three binder compositions listed in Table I below with theircorresponding physical properties are illustrative of the presentinvention.

Table I Ingredients (Percent by weight) Tensile Elonga- ExarnpleStrength tion (p.s.i.) (Percent) CasO DPG TDI TMETN I 36. 0 13.0 26. 524. 5 270 290 II 31. 9 ll. 6 23. 5 33.0 200 III 39. 1 l4. 2 28. 8 l7. 9665 260 IV 32. 5 11.7 22. 4 33. 4 117 191 Table II Cure Cure HardnessTensile Elonga- Sample (Example Time Temp. (Shore Strength tion (Per-IV) (days) F.) Selero (p.s.i.) cent) scope) This data shows that aftertwo days, the 140 F. curing temperature produces the best binder.

The basic binder formulation may be modified by increasing or decreasingthe percent of trimethylol ethane trinitrate (TMETN). For example, thebinder with no TMETN has a strength of 2500 psi. and 150% elongation;the binder with 30% TMETN has a tensile strength of 200 psi and anelongation of 200%. Furthermore, other nitrated plasticizers such asdiethylene glycol dinitrate, 1,4-butanediol dinitrate, polyglycidalnitrate, and pentaerythritol trinitrate may be substituted fortrimethylol ethane trinitrate.

All or part of the dipropylene glycol may be replaced with polypropyleneglycol.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is: 1. A binder composition comprising the followingingredients:

Ingredients: Percent by weight Castor oil 30 to 40 Dipropylene glycol 11to 15 2,4-tolylene diisocyanate 20 to 30 Trimethylol ethane trinitrate15 to 35 2. The composition of claim 1 wherein a mixture of equalamounts of dipropylene glycol and polypropylene glycol are used in lieuof dipropylene glycol.

3. A binder composition consisting essentially of the followingingredients:

4. A binder composition consisting essentially of the followingingredients:

10 Ingredients: Percent by weight Castor oil 36.0 Polypropylene glycol13.0 2,4-tolylene diisocyanate 26.5 Trimethylol ethane trinitrate 24.5

No references cited.

1. A BINDER COMPOSITION COMPRISING THE FOLLOWING INGREDIENTS: